'Comb on a chip' behind new atomic clock design

California, July 23 (IANS) In a first, researchers have demonstrated a new design for an atomic clock that is based on a chip-scale frequency comb or a microcomb.

The microcomb clock is the first demonstration of all-optical control of the microcomb, and its accurate conversion of optical frequencies to lower microwave frequencies.

Optical frequencies are too high to count but microwave frequencies can be counted with electronics.

"The microcomb clock is one way we might get precision frequency metrology tools out of the lab and into real-world settings," said Scott Diddams from the National Institute of Standards and Technology (NIST) in Maryland.

Frequency combs produce precisely defined frequencies of light that are evenly spaced throughout the comb's range.

The name comes from the spectrum's resemblance to the teeth of a pocket comb.

A microcomb generates its set of frequencies from light that gets trapped in the periphery of a tiny silica glass disk, looping around and around the perimeter.

These combs can be astonishingly stable.

"NIST has an ongoing collaboration in this area with researchers from California Institute of Technology (Caltech) who made the two-millimeter-wide silica disk that generates the frequency comb for the new clock," Diddams informed.

The new clock architecture might eventually be used to make portable tools for calibrating frequencies of advanced telecommunications systems or providing microwave signals to boost stability and resolution in radar, navigation and scientific instruments.

The technology also has potential to combine good timekeeping precision with very small size.

The comb clock might be a component of future "NIST on a chip" technologies offering multiple measurement methods and standards in a portable form, said the study which appeared in the journal Optica.